Hammerite Waxoyl Rustproofing for Cars 5L Black. Waxoyl clear is a thick, waxy fluid saturated with a very powerful rustkiller. Spray it on metal and it instantly chases out moisture and forms a flexible weatherproof skin that does not crack, dry out or wash off in the rain. For use with a spray gun.Kills old rust and prevents new rust. Apply to the insides of doors, behind sills and chassis and anywhere that water is likely to collect. Also available in Clear.